Well if you guess NO. your were correct lol.

Sounds like you need the spacer on the drive shaft. Take one of the plastic "bearings" out, and make one out of a piece of cardboard from a serial box/note card. Place it between the original plastic bearing and the red gear, This should put enough pressure on it to stop it from missing the teeth, Grease never hurts either.

I think i have a spare set of skyline mirrors PM me for details.

but back to the FET's yes if you run to big of motor you will fry your stock FET's so you have to upgrade them to one that can handle more power, (stacking them is even better yet) so then your able to run larger motors.

theres a few people on here that will stack FETs for ya for a decent price, just search around, theres also tutorials on it if you want to try it your self (hope you have a steady hand and a good eye, its a pain lol) but to purchase a good set of FETs for a 2x2 stack will run ya 14 bucks shipped + installation.
Lithiums will run ya anywhere from 20-60 bucks depending where you buy from.

But if u need help and cant find something. just ask!